Engine carburetor with a choking and priming control



y 8, 1956 R. s. EVINRUDE 2,744,736

ENGINE CARBURETOR WITH A CHOKING AND PRIMING CONTROL Filed Dec. 9, 1952 INVENTOR. naw? .5. El/flVE 00E AJZAMAW ATTOQNEYS ENGINE CARBURETOR WITH A CHOKING AND PRIMING co TRo 15 Claims. (Cl. 26134) This invention relates to an engine carburetor with a choking and priming control.

j United States Patent U r I Patented May 8, 1956 Fig.-2 is a 'view taken in section on the lines '2--2'-of Fig. 1, portions of the choke valve lever system being omitted. V

Fig.3 is a detailed view in perspective of choke valve operatingparts; I

Fig. 4 is a'view taken in section'on'the line 44 of The carburetor chosen to exemplify the invention is a generally conventional type'which, as best shown inFig. 4, has afloat bowl 5 containing a float 6 and-fromwhich' passage 7 opens, subject to the control of needle valve 8, intothejet9. i

Jet 9 projects into the venturi throat 10 between the air inletpassage 11 and the throttle valve passage .12 at the .outlet of the carburetor. While it formsno part of the present invention, it may be noted that theauxiliary The invention is particularly intended for two-cycle engine carburetors of outboard motors, but its utility is V by no means thus limited. The object of the invention is to provide a single control for both choking and primingfwhich, lnone continuous movement carried to a position'for effecting maximum choking, will thereupon inject priming fuel, desirably from the outside of the carburetor through an opening in the choke valve; The control desirably comprises a reciprocable handle which, during a part of its stroke, controls the choke only. Onlyafter the handle is moved beyond normal choking range does it effect priming.

In'the priming operation, I desirably employ a valveless pump comprising a displacement plunger which moves through one seal toward another. 'In open communication between the two seals, the path of the plunger is completely exposed to the float chamber. Consequently, the normally retracted position of the plunger with respect to said other seal allows free access of fuel from the float chamber to the space beneath the last mentioned seal and in the path of the plunger. opens the priming tube. As the plunger advances through the last mentioned seal, ittraps fuel beneath it and its continued movement expels such fuel forcibly through the priming tube. I have thus I provided a valveless pump or, in diflerent aspects, a pump in which the plunger packing comprises the valve. I

There is considerable advantage in operating the primer in the course of an extension of the same movement which operates'the choke. Not only does it eliminate a From this space separate control, but it also eliminates any need for con- 1 scious thought on the part of the operator, since both the choke and the primer have the function of providing extra fuel for starting and the requirement for priming is simply an enlargement of the requirement for choking'; The" greater the need for excess fuel, the greater will be the amount of fuel supplied, until, ultimately, raw fuel is injected-directly into the carburetor as the primer becomes operative.

" There is an important advantage also in effecting such injection from the exterior of the'carburetor, the air passages being left entirely free of auxiliary ducts which might otherwise require valve controL- It is customary to provide a small central opening in the choke valve for the admission of such air as is required to support combustion. The jet of priming fuel enters through the same hole.

It is important that the choke valve is closed impositively through a tension spring and'is unbalancedto'be opened automatically by air pressure in the event "the engine starts, thus enabling engine operation duringthe p of the idling operation of the engine to which the carburetor is applied, substantially all of the air required by the engine being forced to pass through duct 17 at the outer side of valve 20 into chamber 15 and outthrough duct 18 to the engine side of throttle valve 20 when the latter is closed In. chamber 15 ,the air will pick up its requirement of fuel as determined by the setting ofneedle valvev The v throttlevalve 20 is mounted on a rock shaft 21 having external control lever 22 best illustrated in Fig. 2. 1 v In the admission passage 11 of the carburetor, there is another, rock shaft 23 at a somewhat lower level which supportsthe normally open choke valve 24. This valve normally lies .below the level of the jet tubev9, but as it closes toward the. dotted line position shown in Fig.; 4,-it gradually shuts off the ingress of air, thereby increasing the extent towhich engine vacuum is exerted on the jet tube; In the fully closed position of choke valve 24, sub-, stantially the only air admitted is received through the central port 25 .in. such valve. The rock shaft '23upon which choke valve, 24 oscillates is externally provided, as shown in Fig. l, with an arm at 27 urged by tension spring 28 against the finger 29 of a lever 30. This lever is pivoted at 31 to a suitable bosson the carburetor body 32 A'finger. 33 at .the upper end of lever 30 projects into an opening 34 in the manually operable control slide 35 to receive motion therefrom. This slide is rectilinearly reciprocable inways providedby the guide bosses 36 and 37 on thecarburetor body. vIn thecourse of its reciprocation'it oscillates lever 30 thereby transmitting oscillatoryv closing rno vernent to the choke valve 24 through spring. 28. x

.The arrangement is such that the closing of the check valve is impositive. 1 The spring has sufiicient bias to hold the valve shut during the starting of the engine. As soon as the engine starts,the pressure of air entering the carburetor .will open, the valversuificiently to provide aderegardless of the extreme position at which the slide comes to rest. The shallow notch 39 defines a position in which the choke valve is substantially closed, but the primer hereinafter described has not yet begun to operate.

iln the normaLretracted position'of the slide .in which it is illustrated in Fig. l, the slide does not interfere with throttle valve 2th The throttle valve rock .shaft 21 is extended toward the side of the carburetor shown .in;Fig. l=.and.provided with a rocker arm 41 which normally clears slide 35 by reason of the recess 42 cut into the lower marginof the slide. However, for better performance of the ;,particular engine for which this'carburetor was designed, the contour of theslide at 42 issuch thatas the slide, is. withdrawn toward .its extreme position, iit'will engage arm 41 to constrain the clockwise oscillationof the throttle valve rock shaft 21, as viewed in Fig. l (counterclockwise as viewed in Fig. 4), to somewhatopen the throttle valve andthereby to admit enough air to pick up ..the:relatively heavy :charge of fuel injected by the priming imechanism'presently to be described.

:A cylinder boss 44 cast onto the side of the float bowl 5, as .b'estshown in Figs. 1 and 2, carries a reciprocable priming plunger 45 which, in the normally retractedpositionof the'manually operable slide 35 occupies the elev-atediposition in which it is shown in Fig. 2. If the cylinder boss extends to a sufficiently high level, the plunger will need no upper packing. As shown, it is desirable to provide upper packing for the cylinder at 46 preferably in the form of an Oring mounted in agroove undercut in the cylinder.

"The cylinder portion 47 which is below'the normally retracted position of plunger 45 opens into apressure chamber 48 from which a duct 49 (Fig. 1) leads upwardly to the priming tube 50. The free end of this tube extends around in front of the inlet passage 11 of the carburetor and is directed as a nozzle toward the positionof 'the'aperture 25 in choke valve 24 in the closed position of the choke valve. The chokevalve is alwaysin its "closed position before the priming mechanism acts. (Eonsequently any fuel projected from the delivery end of pipe 50 is necessarily projected through port '25 into the carburetor inlet.

Intersecting the cylinder bore in'which theplunger 45 is 'reciprocable is a passage'52 which opens directly from the carburetor bowl through the cylinder portion 47 into the displacement chamber 48. Upon reciprocation of plunger 45, the plunger first closes ofi communication between passage 52 and chamber 48 by 'entering'the portion '47-ofits cylinder. Here it preferably encounters an G ting seal at 53,*the O-ring being mounted in the undercutgroove 54 in cylinder portion 47. 'Movement of the plunger to and from the O-ring acts like a valve to isolate one charge of fuel in chamber 48 from the float chamber 5, and subsequently to re-open communication 'o'f-chamber'48 with float chamber to receive a further charge of fuel.

The plunger is operated directly from the manually operable slide 35. For this purpose the slide is provided at its rear end with a cross pin at 55 which engages the slotted end of arm-56 on rock shaft 57. The forked arm 58- on'rock shaft57 engages aperipheral groove 59in the upper end of plunger 45 so that, upon forwardmovement of slide 35 the plunger will be caused to move downwardly. The operation is as follows: the position of throttle valve 20 'during the choking and primingoperation is immaterial except for the provision made for opening the throttle valve slightly if'it is fully'closed during priming.

"In starting, or any other condition when engine fuel is inadequate, the operator pulls forwardly on the handle 'of'slide 35. The first effect of forward slidemovem'ent is'to' 'communicate oscillatory motion to the choke'valve --24=t]1rongh *the lever '30 and arm 27 "and intervening tension-spring 2'8 inadirection to-close the choke. -At

the same time, downward motion is communicated to plunger 45 through rock shaft 57 and its arms 56 and 58. However, until the plunger engages the seal at 53, its motion will not effect any priming action.

Meantime, the choke valve will approach its completely closed position, as shown'in dotted lines in Fig. 4. If, by that time, the fuel supply to the engine seems adequate, the operatorwill not continue'to pullforwar'dly on the slide 35 but may return the slide to its initial position, thus relieving the choking action ofchoke valve 24. However, if the fuel supply is still inadcquatelfor starting with the slide 35 advanced suificiently far' to close the choke valve, the operator will continue to pull forwardly upon the slide, whereupon plunger '45 "will enter O-ring seal 53 and begin to displace .fuel from chamber 48 through duct 49 and injection tube 50, whereby a stream of such fuel is injected through the port 25 directly into the carburetor. It will be remembered that at the time of such injection the cam surfaceof the slide 35 at 42 will act on arm 41 if the'throttle valve is closed to elfectat least a partial opening .itselfso'that the engine will draw'enough air to take care of the priming fuel thus injected.

Since the choke valve will have reached its'extreme position before the priming operation occurs, lost. motion is. provided between finger 29 and arm 27 which permits the slide actuated lever 30 to advance independently .of such arm against the tension of spring 28.

.Movement of the control slide 35 from its advance position at the right in Fig. 1 toward its retracted position in which it is illustrated toward the .left in Fig. 1, will first retract plunger 45 with concurrent contraction ofspring 28 until finger 29 engages the outwardly. turned end of arm 27. Thereupon, the continued leftward movement of slide 35 will further retract plunger 45 until it clears theO-ring 53, thereby admitting into chamber 48 afresh charge of fuel from the carburetor bowl or float chamber 5 to replace that discharge therefrom .by plunger action. Concurrently with retractive plunger movement from its extreme position, the choke valve will be moved by lever 30 and arm 27 toward its wide open positionshown in Fig. 3 until finally the parts are at rest in the positions illustrated in these views.

I claim:

1. In a carburetor having an unbalanced choke valve tending to open responsive to unbalanced pressures and a primer, a single control having connections tothechoke valve and the primer for the consecutive operation thereof, the connection of the control tothechoke valve comprising a spring whereby the choke valvemayopen independently of movement of said control. in -.a choke valveclosing direction, a spring anchor andmeans interconnecting said anchor to said control. for movement of theanchor in a direction to maintain substantiallyconstant tension on saidspring notwithstanding such movement of thecontrol.

2.'In a carburetor having an air inlet and a choke valve mounted in the carburetor adjacent the inlet .and provided with an aperture, the combination with achoke valveactuator operatively connected with said valvefor movement thereof betweenits .open and closed positions, a primer pump comprising a cylinder, a plunger,.-and .an injection tube from said cylinder to apositioninfront of said carburetor inlet and directed toward thechoke valve aperture and motion transmitting connectionsfrom said actuator to said plunger mechanically actuating said plunger to inject fuelinto said aperture inthe-same.direction of actuator movement in which. said chokevalve-is closed.

3. Thexdevice-ofclaim .2 in which theroperatingrconnections between said actuator and :the. choke valve and plunger respectively include means whereby" theplunger injects fuel through said aperture in a range-of actuator movements which-is subsequent to the range of actuator movements in which said choke valve is closed. i

In a carburetor having a float bowl and -an air inlet passage, a primer comprising the combination with va cylinder mounteddirectly on the carburetor and having a gravity-flow conduit leading to it from the bowl and communicating with the cylinderat an intermediate point, a plunger normally retracted in said cylinder to a position on one side of said point to leave said conduit in open communication with said cylinder and reciprocable to the other side of said point, a duct leading from said cylinder at said other side; of said pointand comprising a delivery pipe extending externally of the carburetor and directed into said air inlet passage and means for actuating said plunger from its normally retracted position across said point of communicationand therebeyond to displace'fuel trapped in the cylinder-beyond the point ofcommunication to effectthe discharge'thereof under pressure of the plunger through said pipe into said inlet passage. I

a 5 The device of claim 4 in further combination with an annular seal fixed in said cylinder beyond said pointof communicationwith the carburetor bowl to receive said plunger and through and beyond which said plunger advances for the discharge of fuel through said pipe.

6. In a carburetor having a float bowl and an air inlet passage, a primer comprising the combination with a cylinder communicating at an intermediate point with said bowl, a plunger normally retracted in said cylinder to a position above said point, a duct leading from said cylinder below said point and comprising a delivery pipe extending externally of the carburetor and directed into said air inlet passage and means for actuating said plunger from its normally retracted position across said point of communication and therebyond to displace fuel trapped in the cylinder below the point of communication to effect the discharge thereof under pressure of the plunger through said pipe into said inlet passage, in further combination with a carburetor choke valve mounted for oscillation in the inlet passage and provided with an opening to admit air despite the closed position of said valve, said pipe being directed toward said opening to project fuel therethrough.

7. In a carburetor having a float bowl and an air inlet passage, a primer comprising the combination with a cylinder communicating at an intermediate point with said bowl, a plunger normally retracted in said cylinder to a position above said point, a duct leading from said cylinder below said point and'comprising a delivery pipe extending externally of the carburetor and directed into said air inlet passage and means for actuating said plunger from its normally retracted position across said point of communication and therebeyond to displace fuel trapped in the cylinder below the point of communication to efiect the discharge thereof under pressure of the plunger through said pipe into said inlet passage, in further combination with a carburetor choke valve having an actuator operatively connected with the actuating connections for said plunger and having connections to said valve, the respective connections to the valve and plunger comprising means for substantially closing the valve before the plunger advances beyond said point, whereby the choke valve and primer are sequentially effective upon the continuous movement of a single actuator.

8. In a carburetor having an air inlet passage, a fuel supply chamber having a nozzle leading to said passage and an apertured choke valve mounted in said passage in the path of air moving toward said nozzle, the combination of a cylinder mounted at the side of said chamber and communicating at an intermediate point with said chamber, a plunger reciprocable in the cylinder across and beyond said point of communication, means for sealing the plunger to the cylinder beyond said point, means providing a conduit leading from said cylinder beyond said point to a position forwardly of the carburetor and directed toward the position of the choke valve aperture in the closed position of the valve, an actuator provided with a mounting on said carburetor for forward and backward movement, an

16 actuatingconnection from th e actuator tothechoke valve for the movement of said valve'between open and closed position, an actuating connection from the actuator to the plunger for the movement thereof between a. normally retracted position and an advance position beyondfsaid point of communication andbeyond said sealing means from said retracted position, said connections comprising means whereby saidchoke' valve and plunger are effective sequentially for choking and priming, said carburetori,

9. The device of claim 8 in which the actuating conneck tions from the actuator to the/choke valve comprise lost motion connectionsfor permitting continued advance of the plungerand actuator after the choke valve has reached its closed positionv V Y 10; The device of claim 8.inwl1'ich said actuator comprises a slide for which said carburetor is provided with i w y f f f i '11.. In a carburetor having a float chamber and an air inlet passage, a 'boss at the side' of the float chamber provided with a" cylinder, said boss and chamber having a' passage leading from alower portion of the floatchamber into'said cylinder at apoint intermediate the ends there'- of, a plunger normally retracted into one end of the cylinder, a discharge pipe leading from the other end of the cylinder to said air inlet passage, the said other end being substantially closed save for said pipe and adapted to receive fuel from said float chamber through said passage in the retracted position of the plunger, said cylinder having annular packing means adapted to receive and provide a seal for said plunger and disposed in the portion of the cylinder between said passage and the closed end thereof whereby the advance of said plunger in said cylinder in advance of said packing means will have no effect on the fuel in the cylinder, but advance of said plunger beyond said packing means will displace fuel positively from said cylinder through said pipe.

12. In a carburetor having a choke valve and an air passage, the combination with a positive displacement priming fuel pump and means providing a fuel discharge line from said pump into said passage, of a choke valve for restricting air flow through said passage, means for actuating said valve, means for actuating said fuel pump to force a measured charge of fuel through said line into said passage, and a single control having means for the successive operation of the choke valve actuating means and the primer pump actuating means, said control having an impositive spring connection with said valve actuating means whereby said valve is closed impositively, said valve having an unbalanced rockshaft mounting upon which said valve may open in opposition to said impositive connection, subject to air movement through said passage.

13. In a carburetor having an air passage, the combination with a rock shaft spanning the passage in an off center position and a choke valve having an unbalanced mounting on said rockshaft and movable in the oscillation of said shaft between an open position in which said valve is substantially parallel to air flow through said passage and a closed position in which said valve is transverse to the direction of flow and is subject to unbalanced pressures in the event of such flow, an arm on said rockshaft and a lever engageable with said arm in a valve opening direction, and a spring connecting the lever with the arm and comprising an impositive means for transmitting motion to said arm and for tensioning the spring and transmitting motion to said rockshaft in a valve closing direction when the lever is moved in a valve closing direction, whereby said valve may open in response to unbalanced pressures thereon irrespective of the position of said lever, said lever having a positive connection with said arm for transmitting motion to said rockshaft in a valve opening direction.

14. In a carburetor having an air passage, the combination with a rock shaft spanning the passage in an 7 err "center -poSitiona'nd a choke 'valvehaving "an unbalanced mounting ;on said rocksha'ft and -movable inthe oscillation ofsaid :shaft between an open position in which said 'valve 'is "substantially parallel to air flow through said passage and a closed position in which said valve is-transverse'to the.direction of'flow and is subject to'nribalance'd pressures in the event of such 'flow,'an arm on said rockshaft and a lever engageable withsaid arm in a valve opening direction and. having an impos'itive springconnection with said arm for transmitting motion to said rock'sha'ft in a valve closing direction, whereby said valve may open in response to unbalanced pressures thereon irrespective of the position of said lever, said'lever having a positive connection with said arm for transmitting motion to said 'rocksha'ftrin a valve opening-direction, in'further combination with a manually operable control connected withrsaid lever, a fuel priming pump'having a fuel delivery .pipe leading to said passage'beyond said valveiand. motion transmitting.connections from said. con- .trol to said pump for the discharge of fuel-into said passage: subsequent totheclosingrof-said valve, the-said im- "-8 positive connection between'said'leverandarm' permitting continued movement of said control 'and lever "for the actuation of said' pump "after said -valve 'is closed.

15. The 'device o'f claim l4 inwhich said 'valve is provided 'with an air admissionmort and'the 'fuel'delivery conduit from said 'purnp "comprises a nozzle directed through said 5 port into' a portion of said passage beyond the valve.

"keferencesCited-in the tile of this patent UNITED STATES PATENTS .-1,13 1,-37l :Hatfield ,Mar.-9, 1915 1,468,162 LeMaire Sept. 18,-1923 1,624,139 Kettering -Apr.;12,;1927 1,865,561 Fur-gason July,5 ,;1932 2,040,945 Leuschner May 19, 193.6 2,065,167 Wirth' et.al Dec. 22, 1936 2,489,494 .Martin Nov. 29,1949 ,2,5 23,798 Winkler -Sept. .26, 1950 2,564,113 :Kitfler Aug. 14, :1951 ,9 Jorgensen-etal May 10,1955 

